1. Field of the Invention
The present invention relates to a white light emitting diode, and more particularly to a white light emitting diode, into which active layers for respectively emitting red, green and blue light are integrated, and a method for manufacturing the white light emitting diode.
2. Description of the Related Art
As well known to those skilled in the art, white light emitting diodes are widely used as backlights of lighting apparatuses or display units. Methods for manufacturing a white light emitting diode are mainly divided into two types, i.e., a method using a luminescent material and a method simply combining blue, red and green LEDs, which are respectively produced.
First, the method for manufacturing a white light emitting diode using a luminescent material is divided into a method using a blue light emitting diode and a method using an ultraviolet light emitting diode. For example, in the method using a blue light emitting diode, blue light is inverted in terms of wavelength into white light using a YAG (Yttrium-Aluminum-Garnet) luminescent material. That is, the blue light emitted from a blue LED excites the YAG luminescent material, thus allowing a manufactured device to emit white light.
FIG. 1a is a schematic cross-sectional view of a conventional white light emitting diode 20 using a YAG luminescent material. With reference to FIG. 1a, the white light emitting diode 20 comprises an InGaN blue LED 10 mounted on a cap of an anode lead frame 12, and a YAG luminescent material 15 surrounding the InGaN blue LED 10 within the cap. The InGaN blue LED 10 is connected to the anode lead frame 12 and a cathode lead frame 14 by wires 11 and 13, respectively. The upper surfaces of the lead frames 12 and 14, on which the InGaN blue LED 10 is mounted, are molded with a transparent material 17.
Power is supplied to the InGaN blue LED 10 through the lead frames 12 and 14, so that the InGaN blue LED 10 emits blue light. A part of the emitted blue light excites the YAG luminescent material 15. Here, the YAG luminescent material 15 is characterized in that it is excited at a peak wavelength (460 nm) of the InGaN blue LED 10, thus emitting fluorescent yellowish green light. The fluorescent yellowish green light obtained from the YAG luminescent material 15 is combined with the remaining part of the blue light emitted directly from the InGaN blue LED 10, thereby being finally emitted as white light.
The conventional white light emitting diode 20 shown in FIG. 1a is advantageous in that it does not require current regulation to be adapted in use of LEDs respectively emitting RGB (Red/Green/Blue) light. Similarly to the above method for manufacturing the conventional white light emitting diode 20, there are a method using an ultraviolet light LED and a method using RGB light luminescent materials in combination.
However, in case that the wavelength modulation is employed as described above, there are drawbacks such as the reduction of optical efficiency in exciting the luminescent material and the reduction of a color correction factor.
There is another conventional white light emitting diode using RGB LEDs. FIG. 1b is a schematic cross-sectional view of a conventional white light emitting diode 30 using RGB LEDs. With reference to FIG. 1b, the white light emitting diode 30 comprises three LEDs 23, 25 and 27, which are produced as components. The LEDs 23, 25 and 27 are mounted on a single printed circuit board 21 via wires 22. The white emitting diode 30 shown in FIG. 1b emits white light by combining different lights (for example, R, G and B light) emitted from the respective LEDs 23, 25 and 27.
Such a white light emitting diode eliminates problems raised by the use of the luminescent material, thus obtaining excellent color sensitivity. However, the above white light emitting diode requires plural LEDs, thereby increasing the production cost. Further, the above white light emitting diode must regulate the current supplied to respective LEDs so as to obtain the desired white light, thus requiring a complicated circuit configuration.